gh-130706: Add a fast path to _Py_Dealloc() for non-GC objects. (gh-158645)

Author: corona10

Misc/NEWS.d/next/Core_and_Builtins/2026-10-03-19-11-03.gh-issue-130706.01-O6U.rst

@@ -0,0 +1,2 @@
+Add a fast path to ``_Py_Dealloc()`` for non-GC objects. Patch by Donghee
+Na.

Objects/object.c

@@ -3306,8 +3306,8 @@ next" object in the chain to 0.  This can easily lead to stack overflows.
 To avoid that, if the C stack is nearing its limit, instead of calling
 dealloc on the object, it is added to a queue to be freed later when the
 stack is shallower */
-void
-_Py_Dealloc(PyObject *op)
+static Py_NO_INLINE void
+py_dealloc(PyObject *op)
 {
     PyTypeObject *type = Py_TYPE(op);
     unsigned long gc_flag = type->tp_flags & Py_TPFLAGS_HAVE_GC;
@@ -3372,6 +3372,28 @@ _Py_Dealloc(PyObject *op)
     }
 }
 
+/*
+ * gh-130706: Keep the GC/reftracer path in the non-inlined py_dealloc().
+ * Inlining it makes the compiler save callee-saved registers at entry,
+ * so the non-GC objects path would have unnecessary register spills.
+ */
+void
+_Py_Dealloc(PyObject *op)
+{
+#if !defined(Py_DEBUG) && !defined(Py_TRACE_REFS)
+    // gh-130706: Avoid unnecessary register spills for non-GC objects.
+    PyTypeObject *type = Py_TYPE(op);
+    if (_PyRuntime.ref_tracer.tracer_func == NULL
+        && !(type->tp_flags & Py_TPFLAGS_HAVE_GC))
+    {
+        type->tp_dealloc(op);
+        return;
+    }
+#endif
+    // GC objects (trashcan), reftracer set, or debug builds.
+    py_dealloc(op);
+}
+
 
 PyObject **
 PyObject_GET_WEAKREFS_LISTPTR(PyObject *op)